CBR900RR Fireblade Performance Modifications

Inside this Newsletter
CBR900 Hot up

Stage 1,2 & 3

Boy have we had our work cut out over the last few months. It never rains
but it pours. One of our mechanics "Stripper" went on a bike rally and
didn't quite make it, in fact he is lucky to be alive, breaking his back
in 4 places. Surprising as it seems, he was only out of action for about
2 months, it doesn't seem to have slowed him down though. Everyone has
had a dose of that nasty flu which puts you on your back for about a week
and takes another 2 weeks to fully recover from. Steve thought he was pretty
cool managing to avoid it initially and giving us a hard time for being
big nanaís until he finally caught it. No price for guessing who
was the biggest nana of all. And just to top that off the entire
block which our shop is a part of was sold to a property developer who
in turn made about half a mill when he sold it to JB Hi Fi, less than 4
months later, ( we're in the wrong business). So you might say we have
had some work to do. The new shop will be a lot more permanent than this
one because we own , or I should say the Bank owns it. We will be here
right up to Xmas, then over the break move it all over to the new factory
ready to open in January. The new address is on the back of this news.
This is a new subdivision and although not main road is easy to find. Just
look for the Sandbelt Hotel on South Road, turn left or right onto Bignell
road, depending on which way you're travelling and 200 metres on the left
is Winston court. Melways ref map78 A6.

Ride day update.

The Broadford ride day was held in November, though it did rain most
of the morning it turned out to be a good thing because Steve Brouggy from
Australian
Superbike School spent that time talking about basic suspension set
up in terms that everyone could understand and apply in the afternoon when
it cleared up. There has not been any date set for the next one, but we
will keep you up to date when they are confirmed.

CBR900 Hot up

This has got to be one of the best bikes to hot up because of the really
good increases in horse power that is obtainable. The ports in the cylinder
head are small in comparison to a ZX7-9 or GSXR7 making it more suitable
for porting and gas flowing and is generally easy to work on from a mechanics
point of view. Complete dis assembly of the engine for cylinder boring
is not ideal but well worth the effort and money spent.

This job has 3 stages to suit your own needs and the size of your pocket
when it comes to shelling out the bucks, and can be added to at a later
date when or if you desire. The CBR900 is never going to be an R1 beater
but it will certainly hold its own with the Stage 3 kit fitted and provide
many hours of adrenaline rushing ball tearing fun.

Stage 1

Stage 1 consists of a Hindle complete exhaust system, Dynojet carb kit
and K&N air filter. The dynojet setting does vary from bike to bike
which is why we like to dyno them to fine tune the kit. If that isn't possible,
or you're interstate then the recommended settings in the kit will get
you very close to the mark.

This example shows a stock figure of 118hp before we started working
on it, (stock power for a CBR900 varies from 110 up to 118 hp). After fitting
above mentioned parts and tuning to suit it finished up with a peak of
124 hp but more importantly a good 5-6 through the midrange where it is
needed most. See graph below

.

The other aspect of this Stage is throttle response and acceleration.
This is the single most important test because it relates to what the rider
feels on the road. Its all about how fast the carburettor slide lifts up
when accelerating at full throttle. The quicker it lifts then the harder
it accelerates, but if it lifts too fast then your left with a hole in
the midrange, so its important to get it right. You're probably wondering
why they don't make them like this from the factory and there's a couple
of reasons for it. To comply for ADR requirements it must pass emissions
tests and noise tests, both exhaust and induction which means they are
limited to how far they can go with it.

The graph below is from the same bike before and after fitting these
parts. Obviously to make more hp it has to burn fuel, so expect an increase
in consumption, it's not huge depending on how you ride but those who measure
their mileage will find an increase. Of course if your too busy riding
it then all you'll notice is the extra power that's on hand.

The price for this kit including Hindle stainless steel pipe, Dynojet
carb kit and K&N filter, fitted, jetted and dyno tuned from $1995.00.
You can bring the price down by not fitting the air filter or jet kit,
you will still get a good result, but if you're really hungry for more
power then that is the go before you get to stage 2.

Big Skid kit Stage 2

Stage 2 includes all of stage 1, porting, flow testing, and setting
the cam timing. The first thing is to remove the cylinder head, set it
up on the flow bench and record the flow readings so we have a base to
work off. This is a very time consuming process because the flow rating
is tested at 5 or 6 different valve lifts which must be measured using
2 dial indicators set up on a hand made plate bolted solidly to the test
head that will give the same measurement and consistency every time a test
is carried out. Depending on how much money is available to spend these
tests may be carried out on all cylinders, inlet and exhaust, with a total
number of 40 to 48 tests all before any re-shaping even starts. Once the
data has been calculated and correction factors factored in it's onto the
job of removing any restrictions in the ports and valve area. It's really
important not to get too carried away with the porting tool as it is easy
to remove metal and difficult to replace, so careful testing is required
all the way through the process. Once the desired figures are achieved
final clean up, seat cutting and re seating is done and the head assembled.
As you will probably now realise this is a time consuming job which at
the end of the day the money available to spend dictates the time spent
in this area. To get a good result 4 - 5 days full time will need to be
spent.

Now we fit the head to the engine and measure valve to piston and squish
clearances before surface grinding the head to bring up the compression
ratio. It's very important to get this right as to much compression means
it wont run on pump fuel or worse still pistons hit valves and drives valves
permanently into cylinder head causing much embarrassment for engine builder.

Once we have a handle on all of that then the head is assembled one
final time, clearances checked and fitted to the engine. Because we have
altered the deck height adjustable cam sprockets are installed and the
cam timing reset using a degree wheel and dial indicator. The final tuning
work can now be done to make sure that all the hard work has paid off in
terms of good usable horse power. Generally these bikes don't need much
jetting work and will run very well without making any carb changes. The
graph below shows the result. Stock we had 113 hp at the rear wheel, with
the
Big SkidKit stage 2 fitted we have a peak of 127hp but
more importantly a good strong improvement right through the rev range.

Skud Kit Stage 3

This is not for the feint hearted, expect to have the front end in the
air more than it is on the ground and if yours is an early model it will
need a good steering damper to keep it from spitting you off. As with the
other 2 kits all that has been done to this point is used as well as a
Big Bore piston kit in either 945cc or 970cc. You can chop and change things
or use your own choice of pipe, carb kit, piston kit, or not use some of
it at all if your budget's tight, but if you want the best dollar
value for performance this is the way to go.

Complete engine strip down and inspection is required, especially in
the main bearing and big end bearing department as the load to these bearings
is seriously increased, if you have the balls to use the extra power
that's on tap. If the mileage is really low then you can get away with
not doing anything, but if you want to improve things then it should all
be balanced including the crankshaft, conrods, and pistons. It's a waste
of time only doing the crank if everything else is out of balance and so
on. Balancing everything is not essential but it does improve overall responsiveness
and smoothness and lessen the possibility of something going wrong. It
doesn't increase horse power! While this is being done the upper crankcase
half which has the barrel cast into it can be bored out to suit the over
size piston kit. Then it's a matter of fitting new bearings if applicable
and checking to make sure that we have the desired oil clearance and that
the piston ring ends are gapped. Once everything has been done final assembly
begins. You may wonder why I said final assembly? It's because the engine
is assembled to certain stages a number of times to check running clearances
and make sure that it wont self distract when its fired up. This is where
a lot of hours are taken up, one engine will take one person from start
to finish including everything talked about in these pages the best part
of one and half to 2 weeks. Now can you see why it costs so much?

When all the blue printing and measuring is complete its pretty much
straight forward assembly work, finishing off by dialling in the cams to
spec. All that is required now is to put 50 kms or so on it to bed in valves
and rings, or if it has had bearings replaced a couple 100 road kmís before
the final tuning is done, after which we should have close to the results
shown in the graph below. Peak horse power has gone from 110 in stock form
to 135 hp but most importantly the midrange has been given a healthy 15-20hp
right through the range, the 970 piston kit is even better again but that's
another story. Price is from $3000.00 not including pipe and carb kit.

And that's about all we have time for, I've been told to get off the
computer as it's about to be turned off and moved to the new shop. So have
a safe and enjoyable break and we'll see you next year.